Relativistic Jets in Collapsars

By Weiqun Zhang, Stan Woosley, UC A.I.MacFadyen, Santa Cruz, Caltech. 2002

308 citations recorded by the source corpus.

We examine the propagation of two-dimensional relativistic jets through the stellar progenitor in the collapsar model for gamma-ray bursts (GRBs). Each jet is parameterized by a radius where it is introduced and by its initial Lorentz factor, opening angle, power, and internal energy. In agreement with previous studies, we find that relativistic jets are collimated by their passage through the stellar mantle. Starting with an initial half-angle of up to 20°, they emerge with half-angles that, though variable with time, are around 5°. Interaction of these jets with the star and their own cocoons also causes mixing that sporadically decelerates the flow. We speculate that this mixing instability is chiefly responsible for the variable Lorentz factor needed in the internal shock model and for the complex light curves seen in many GRBs. In all cases studied, the jet is shocked deep inside the star following a brief period of adiabatic expansion. This shock converts most of the jet's kinetic energy into internal energy, so even initially "cold" jets become hot after going a short distance. The jet that finally emerges from the star thus has a moderate Lorentz factor, modulated by mixing, and a very large internal energy. In a second series of calculations, we follow the escape of that sort of jet. Conversion of the remaining internal energy gives terminal Lorentz factors along the axis of approximately 150 for the initial conditions chosen. Because of the large ratio of internal to kinetic energy in both the jet (≥80%) and its cocoon, the opening angle of the final jet is significantly greater than at breakout. A small amount of material emerges at large angles, but with a Lorentz factor still sufficiently large to make a weak GRB. This leads us to propose a "unified model" in which a variety of high-energy transients, ranging from X-ray flashes to "classic" GRBs, may be seen depending on the angle at which a standard collapsar is observed. We also speculate that the breakout of a relativistic jet and its collision with the stellar wind will produce a brief transient with properties similar to the class of "short-hard" GRBs. Implications of our calculations for GRB light curves, the luminosity-variability relation, and the GRB-supernova association are also discussed.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/86e1d7193d7c1db90d53d93228b865fa82e97a59

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In Astronomy and Astrophysics

1. Bing Zhang
2. E. Berger
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4. Pawan Kumar
5. E. Quataert
6. E. Nakar
7. T. Thompson
8. A. Tchekhovskoy

Citations in the corpus

• AFTERGLOW OBSERVATIONS OF FERMI LARGE AREA TELESCOPE GAMMA-RAY BURSTS AND THE EMERGING CLASS OF HYPER-ENERGETIC EVENTS (2010, background): “Annihilation of νν̄ pairs will produce a gas of hot electron-positron pairs, which, assuming sufficiently low baryon loading, can then rapidly expand in the lowdensity regions along the axis of rotation (a “fireball”, e.g., Zhang et al. 2003).”
• Gamma-Ray Bursts in the Swift Era (2007, methodology): “…polarization, Coburn & Bogg 2003, cf. Rutledg & Fox 2004; Kalemci et al. 2007, the requirement a higherǫB in the reverse shock, Fan et al. 2002; Zhang et al. 2003; Kumar& Panaitescu 2003; Fan et al. 2005c; Wei et al. 2006, as well as the energetics argument for X-ray flares, Fan et al. 2005d)…”
• DISCERNING THE PHYSICAL ORIGINS OF COSMOLOGICAL GAMMA-RAY BURSTS BASED ON MULTIPLE OBSERVATIONAL CRITERIA: THE CASES OF z = 6.7 GRB 080913, z = 8.2 GRB 090423, AND SOME SHORT/HARD GRBs (2009, background): “For example, Zhang et al. (2003) proposed that a short/hard pulse of gamma-ray emission may be associated with eruption of the fireball from the stellar envelope.”
• THE AFTERGLOWS OF SWIFT-ERA GAMMA-RAY BURSTS. II. TYPE I GRB VERSUS TYPE II GRB OPTICAL AFTERGLOWS (2008, background): “Zhang et al. (2003) show that, under special conditions, the jet breakout from the massive star can produce a bright short emission spike, which is then followed by the lower-luminosity long GRB.”
• Low-Luminosity Gamma-Ray Bursts as a Unique Population: Luminosity Function, Local Rate, and Beaming Factor (2006, methodology): “Such a jet configuration is different from the conventional jet-cocoon picture in the standard collapsar model in which the cocoon component is not as broad as 31o (e.g. Zhang et al. 2003).”
• Temporal and Angular Properties of Gamma-Ray Burst Jets Emerging from Massive Stars (2006, methodology): “It seems, however, that our high-resolution simulations were not able to reproduce previous analytic or numerical results like the 2 universal jet of LB05 or the 3 distribution found by Zhang et al. (2003).”
• Supernova hosts for gamma-ray burst jets: dynamical constraints (2002, background): “2 Zhang et al. (2003) suggest equation (38) does not describe their numerical results; however, it is not clear what r conf or j(r conf) is applicable to the wide-angle ejecta they see.”
• The Piecewise Parabolic Method for Multidimensional Relativistic Fluid Dynamics (2005, background): “We adopted a ¼ 1:77, b ¼ 2:6, 0 ¼ 106 g cm 3, and p0 ¼ 8:33 ; 1023 dyn cm 3 to match the progenitor model of Zhang et al. (2003).”
• The Proto-Magnetar Model for Gamma-Ray Bursts (2010, background): “…through the star at a significant fraction β of the speed of light (e.g. MacFadyen & Woosley 1999; Aloy et al. 2000; Ramirez-Ruiz et al. 2002; Zhang et al. 2003; Morsony et al. 2007; Bucciantini et al. 2008), such that it ‘breaks out’ of the stellar surface of radius R⋆ on a timescale tbo…”
• A theory of photospheric emission from relativistic, collimated outflows (2012, methodology): “10 as well as the Monte Carlo simulations for different profile parameters and viewing angles (Figures 6 to 11).”
• The Propagation and Eruption of Relativistic Jets from the Stellar Progenitors of Gamma-Ray Bursts (2003, background): “…in both Newtonian (MacFadyen & Woosley 1999; MacFadyen 365 et al. 2001; Khokhlov et al. 1999) and relativistic simulations (Aloy et al. 2000; Zhang et al. 2003, hereafter Paper I), and it has been shown that the collapsar model is able to explain many of the observed characteristics of GRBs.”
• Simulations of ultrarelativistic magnetodynamic jets from gamma‐ray burst engines (2008, methodology): “The model parameters we consider are motivated by pre-supernova stellar models (MacFadyen & Woosley 1999; Aloy et al. 2000; Zhang et al. 2003; Heger, Woosley & Spruit 2005; Zhang, Woosley & Heger 2008) and GRMHD simulations of turbulent accretion discs (McKinney & Gammie 2004; McKinney & Narayan…”